Well.
Generally speaking, if you get it when you're a kid, it's unpleasant but no biggie.
If you get it when you're a grown-up; rather like other illnesses we were all "supposed" to get when we were nippers, it can be a Thing.
I never had Chicken Pox when I was a kid. I got it when I was 30. It was fucking horrendous.
My GP, to the (now) Ex Mrs S: "The only reason he's not in hospital is because you have young children and it would be harder for you."
The rash on the outside was so bad, both my eyes closed up, and my face was just one mass of pus. The rash on the INSIDE was much worse. Thankfully, I didn't get pneumonia, which is a common complication in adults, but I had dreadful digestive failure, I basically pee'd pus, and the spots in my throat were so dense, I could barely swallow.
My children were so scared of me, they wouldn't come in the room. Turning over in bed was like lying on bubble-wrap - thanks to the popping blisters. My fever was 105 for a week. The ex Mrs S set up a fan on me to keep me cool, and kept me plastered in calamine. That probably helped me a bit.
It took me six weeks to recover.